Work implement linkage system having automated features for a work vehicle

ABSTRACT

A work vehicle including a boom, a work implement, and a linkage sensor system having automated features to move the boom and the work implement. The work vehicle includes a frame, a boom actuator for the boom, a boom sensor to identify a boom position with respect to the frame, an implement actuator, and an implement sensor to identify a work implement position with respect to the boom. A controller receives boom position signals from the boom sensor and work implement signals from the implement sensor. The controller transmits a boom adjustment signal based on the boom position modified by boom sensor calibration values and transmits an implement adjustment signal based on the implement position modified by implement sensor calibration values. The implement sensor calibration values are determined during a calibration process when moving the boom from a lowest position to a highest position.

FIELD OF THE DISCLOSURE

The present invention generally relates to a work vehicle having a work implement, and more particularly to a system and method of automated features for the work implement and a linkage coupled to the work implement.

BACKGROUND

Work vehicles, such as a four wheel drive loader, a tractor, or a self-propelled combine-harvester, include a prime mover which generates power to perform work. Other work vehicles having prime movers include construction vehicles, forestry vehicles, lawn maintenance vehicles, as well as on-road vehicles such as those used to plow snow, spread salt, or vehicles with towing capability.

In the case of a four wheel drive loader, for instance, the prime mover is often a diesel engine that generates power from a supply of diesel fuel. The diesel engine drives a transmission which moves a ground engaging traction device, such as wheels or treads, to propel the loader, in some situations, across unimproved ground for use in construction. Such loaders include a hydraulic machine either powered by the engine or powered by a generator driven by the engine. The hydraulic machine is used, for instance, to raise or lower a work implement, such as a bucket or a fork.

Many, if not all, of these work vehicles, include a linkage attached to the work implement that is moved by the linkage from one position to another position. The linkage is moved either by an operator manipulating a user input device, such as a toggle or a switch, or automatically by a control system located on the work vehicle. In some of these work vehicles, the linkage is moved automatically to move the work implement to one or more predetermined positions. Such predetermined positions are typically positions that are constantly repeated during a work operation. By automatically moving the work implement to the predetermined position, machine operations are improved and operator fatigue is reduced. In some cases, however, due to manufacturing variations in the structure of the linkages and associated hardware, the predetermined positions can vary from machine to machine or can vary over time in a particular machine. When variations occur, the work operations become less efficient and any advantage provide by automated positioning of the linkage and/or the work implement is lost. What is needed therefore is a positioning system to move the linkage and the attached work implement from one position to a next position that maintains consistent and accurate placement of the linkage and/or work implement.

SUMMARY

In one embodiment, there is provided a method of moving a work implement and a boom operatively connected a work vehicle supported by a surface, the work vehicle including a work implement sensor to determine a position of the work implement, and a boom sensor to determine the position of the boom. The method includes: calibrating the work implement sensor; calibrating the boom sensor; raising the boom from a lowered position to a raised position; determining, with the boom sensor, a lowered position of the boom at the lowered position; determining, with the boom sensor, a raised position of the boom at the raised position; identifying a plurality of work implement positions while moving the boom from the lowered position to the raised position; identifying a plurality of error values based on the identified plurality of work implement positions; and moving the boom based on the plurality of error values during a work operation.

In another embodiment, there is provided a work vehicle including a frame, a boom actuator including a boom arm, the boom actuator operatively connected to the frame, and a work implement operatively connected to the boom arm. A boom sensor is located at the boom actuator to identify a boom arm position of the boom arm with respect to the frame. An implement sensor is located at the work implement actuator to identify a work implement position of the work implement with respect to the boom arm. A boom control device provides a boom control signal and an implement control device provides an implement control signal. A control module is supported by the frame and is operatively connected to the boom sensor, the work implement sensor, the boom actuator, and the work implement actuator, wherein the control module receives boom position signals from the boom sensor and work implement signals from the implement sensor, and transmits to the boom actuator a boom adjustment signal based on the boom position modified by a boom sensor calibration value and transmits to the implement actuator an implement adjustment signal based on the implement position modified by an implement sensor calibration value.

In a further embodiment, there is provided a method of positioning a work implement and a boom operatively connected a work vehicle wherein the work vehicle includes a work implement sensor to determine a positon of the work implement and a boom sensor to determine the position of the boom. The method includes: calibrating the work implement sensor and the boom sensor; identifying an initial work implement position at a lowest boom position with the work implement sensor; identifying a plurality of boom positions while moving the boom from a lowest position to a highest position with the boom sensor; identifying a plurality of work implement positions with the work implement sensor at each of the plurality of boom positions while moving the boom from the lowest position to the highest position and while maintaining a position of the work implement with respect to the boom at the initial work implement position; comparing each of the identified plurality work implement positons with the initial work implement position to arrive at a plurality of work implement error values; and positioning the work implement with the boom based on the work implement error values during a work operation.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned aspects of the present invention and the manner of obtaining them will become more apparent and the invention itself will be better understood by reference to the following description of the embodiments of the invention, taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a side elevational view of work vehicle with a work implement in a first position;

FIG. 2 is a side elevational view of work vehicle with a work implement in a second position;

FIG. 3 is a side elevational view of work vehicle with a work implement in a third position;

FIG. 4 is a block diagram of a control system of the work vehicle; and

FIG. 5 is a block diagram of a process to determine position errors in a boom/work implement linkage.

DETAILED DESCRIPTION

For the purposes of promoting an understanding of the principles of the novel invention, reference will now be made to the embodiments described herein and illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the novel invention is thereby intended, such alterations and further modifications in the illustrated devices and methods, and such further applications of the principles of the novel invention as illustrated herein being contemplated as would normally occur to one skilled in the art to which the novel invention relates.

FIG. 1 is a side elevational view of a work vehicle 10. The work vehicle 10 is a four wheel drive (4WD) loader having: a cab 12; a rear body portion 14 with rear wheels 16; a front body portion 20 with front wheels 22, a work implement such as a bucket 24, a linkage 26 for adjusting a position of the bucket 24, a hydraulic cylinder 28, and a hydraulic cylinder 30 (See FIGS. 2 and 3) to power the linkage 26. The bucket 24 is rotatably coupled to a boom arm 31 at a pivot location 32. A second boom arm, substantially similar to the boom arm 31, is not shown but is operatively connected to the bucket 24 at an opposite side of the bucket 24 as would be understood by one skilled in the art. The cylinder 30 and the boom arm 31 provide a boom actuator that raises and lowers the implement with respect to the frame of the vehicle.

An articulation joint 33 enables angular adjustment of the rear body portion 14 with the front body portion 20. Hydraulic cylinders 34, 35, and 36 enable angular changes between the rear and front body portions 14 and 20 under hydraulic power derived from conventional hydraulic pumps (not shown).

An accelerator pedal 38 and a user interface 40 are located within the cab for use by an operator of the vehicle 10. The accelerator pedal 38 enables the operator to adjust the speed of the vehicle. In other embodiments, a hand lever provides this function.

The user interface 40 includes a steering wheel 42, a plurality of operator selectable buttons configured to enable the operator to control the operation and function of the vehicle 10, and any accessories or implements being driven by the powertrain of the vehicle, including the bucket 24. The user interface 40 in one embodiment, includes a user interface screen having a plurality of user selectable buttons to select from a plurality of commands or menus, each of which is selectable through a touch screen having a display. In another embodiment, the user interface includes a plurality of mechanical push buttons as well as a touch screen. In another embodiment, the user interface includes a display screen and only mechanical push buttons.

As illustrated in FIG. 1, the linkage 26 is in a fully lowered position with respect to ground 27. In this position, the bucket 24 is set to a level position with the ground 27 such that a plane defined by a bottom portion of the bucket is substantially flush with the ground and is substantially horizontal. For the purposes of this disclosure, the position of the linkage 26 and bucket 24 in FIG. 1 is considered to be a fully lowered position. The linkage 26, under some conditions, is capable of being lowered further than the illustrated position of FIG. 1 if the surface of the ground beneath the bucket 24 is lower than the surface of the wheels upon which the vehicle is located.

One end of the arm 31 is operatively connected to the bucket 24 at the pivot location 32 and another end of the arm 31 is operatively connected to a pivot location 50 of a frame structure 52. As seen in FIGS. 2 and 3, one end of the cylinder 30 is operatively connected to the boom arm 31 and another end of the cylinder 30 is operatively connected to the frame 52. Extension and retraction of the cylinder 30 adjusts the positon of the arm 31 with respect to the frame 52 to raise and to lower the bucket 24. Using the boom arm 31, the bucket 24 is moved from the fully lowered position of FIG. 1 to a partially raised position of FIG. 2, and to a fully raised position of FIG. 3. The fully raised position of FIG. 3 is determined by one or more of mechanical stops of between the boom arm 31, the cylinder 30, and the frame 52.

The bucket 24 is adjustable with respect to the boom arm 31 by activation of the cylinder 28 having one end coupled to a portion of the vehicle 10, as is understood by one skilled in the art, and at another end thereof operatively connected to an implement link 54. The implement link 54 is rotatably coupled to an end of the cylinder 28 at a pivot location 56. Another end of the implement link 54 is rotatably coupled to a portion of the bucket 24 at a pivot location. An intermediate portion 60 of the link 54 is rotatably coupled to a flange 62 fixedly connected to the arm 31. Extension and retraction of the cylinder 28 rotates the bucket 24 about the pivot location 32. The cylinder 28 and the link 54 provide an implement actuator to move the bucket 24 with respect to the boom arm 31.

A sensor 64 is located at or near the pivot 50 to determine an angle of rotation of the arm 31 with respect to the frame 52. In one embodiment, the sensor 64 is operatively connected to the arm 31 by a four bar linkage as is understood by one skilled in the art. In another embodiment, the sensor 64 is located at the pivot 50. As the cylinder 30 extends and retracts, the arm 31 is raised and lowered with respect to ground 27. A second sensor 66 is located at or near the pivot axis of the link 54 with respect to the flange 62. As the cylinder 28 extends and retracts, the bucket 24 rotates about the pivot axis 32. An output of the sensor 64 is used to determine a height of the bucket 24 with respect to ground and an output of the second sensor 66 is used to determine the inclination of the bucket 24 with respect to the arm 31.

FIG. 4 illustrates a block diagram of an implement control system 100 to adjust a linkage system for positioning the boom arm 31 and the implement 24, with respect to the vehicle 10 based on either manual position commands, automatic position commands, or a combination of manual and automatic position commands. The implement control system 100 includes a controller 102, such as an electronic control unit (ECU), which is connected to a controller area network (CAN) bus (not shown), but represented in FIG. 4 as double arrow lines indicating a communication link over the bus to and from the controller 102 and to the various devices and components of the vehicle 10. The CAN bus is configured to transmit electrical control signals for the control of various devices connected to the bus as well as to transmit status signals that identify the status of the connected devices.

The controller 102, in different embodiments, includes a computer, computer system, or other programmable devices. In other embodiments, the controller 102 includes one or more processors 104 (e.g. microprocessors), and an associated memory 106, which can be internal to the processor or external to the processor. The memory 106 includes, in different embodiments, random access memory (RAM) devices comprising the memory storage of the controller 102, as well as any other types of memory, e.g., cache memories, non-volatile or backup memories, programmable memories, or flash memories, and read-only memories. In addition, the memory includes in other embodiments a memory storage physically located elsewhere from the processing devices and can include any cache memory in a processing device, as well as any storage capacity used as a virtual memory, e.g., as stored on a mass storage device or another computer coupled to the controller 102. The mass storage device can include a cache or other dataspace which can include databases. Memory storage, in other embodiments, is located in the “cloud”, where the memory is located at a distant location which provides the stored information wirelessly to the controller 102. When referring to the controller 102 and the memory 106 in this disclosure other types of controllers and other types of memory are contemplated.

The controller 102 executes or otherwise relies upon computer software applications, components, programs, objects, modules, or data structures, etc. Software routines resident in the included memory of the controller 102, or other memory, are executed in response to the signals received from sensors as well as signals received from other controllers or ECUs such as an engine ECU and a transmission ECU. The controller 102, in one or more embodiments, also relies on one or more computer software applications that are located in the “cloud”, where the cloud generally refers to a network having stored data and/or computer software programs accessed through the internet. The executed software includes one or more specific applications, components, programs, objects, modules or sequences of instructions typically referred to as “program code”. The program code includes one or more instructions located in memory and other storage devices which execute the instructions which are resident in memory, which are responsive to other instructions generated by the system, or which are provided a user interface operated by the user.

Moreover, while the invention is described in the context of controllers, those skilled in the art will appreciate that the various embodiments of the invention are capable of being distributed as a program product in a variety of forms, and that the invention applies equally regardless of the particular type of computer readable media used to actually carry out the distribution. Examples of computer readable media include but are not limited to physical, recordable type media such as volatile and non-volatile memory devices, floppy and other removable disks, hard disk drives, optical disks (e.g., CD-ROM's, DVD's, etc.), among others, and transmission type media such as digital and analog communication links.

In addition, it should be appreciated that the process or processes described herein are implementable in various program code and should not be limited to specific types of program code or specific organizations of such program code. Additionally, in view of the typically endless number of manners in which computer programs may be organized into routines, procedures, methods, modules, objects, and the like, as well as the various manners in which program functionality may be allocated among various software layers that are resident within a controller or computer if used, (e.g., operating systems, libraries, APIs, applications, applets, etc.), it should be appreciated that the invention is not limited to a specific organization.

The vehicle 10 includes a plurality of sensors, each of which in different embodiments, identifies vehicle device status and transmits sensor information to the controller 102, which the controller 102 executes to adjust the position the boom arm 31 and the implement 24. When moving the boom arm 31, the controller 102 adjusts the position of the cylinder(s) 30. The controller 102 adjusts the position of the cylinder(s) 30 to move the implement 24 with respect to the boom 31.

The controller 102 generates commands to adjust the position of the arm 31 based on sensor information received from the arm sensor 64 and adjusts the position of the implement 24 based on sensor information based on the implement sensor 66.

The controller 102 is further operatively connected to the operator user interface 40 that includes a display 110, a boom control 112, an implement control 114, and a return to dig feature control 116. The boom control 112 is a user controlled actuation device, such as a toggle, for moving the boom 31. The implement control 114 is a user controlled actuation device for moving the implement 24, such as another toggle. The return to dig 116 is an actuation device, such as pushbutton, which when activated is used to move the bucket 24 and the arm 31 to a return to dig position such as that illustrated in FIG. 1. The display 110 provides a display screen to display vehicle status information including a real time identification of the height of the boom and the inclination of the implement. The display 110 further includes user input buttons of one or more different types including touch screen buttons, contact buttons, or physically manipulated buttons. In one or more embodiments, operator user interface includes an identify implement user input 111 that displays a number of different types of implements capable of being used by the vehicle 10. In some embodiments, the results of the calibration routine depend on the type of work implement being used. For instance in one example, the determined calibration values for the calibration routine of a bucket are different than the calibration values for the calibration routing of a fork. The identify work implement user input is used to identify which type of work implement is being used such that different calibration values are determined for different types of work implements. In some embodiments, the kinematic model being used in the calibration routine depends on the type of work implement being used. Consequently, selection of the type of work implement instructs the control module 102 as to which kinematic model is to be used.

The memory 106 is organized as addressable memory such that sensor information is stored as data for both the boom and implements at addressable memory 108. The data stored in memory 108 includes positional data of the boom 31 as it moves from a lowest position to a highest position. The data stored in memory 108 further includes actual positional data of the implement 24 as it moves between a fully extended position to a fully retracted position. The memory 106 further includes kinematic data in memory 110 for the entire kinematic chain of both driven and driving components that include the boom 31 and the implement 24. The kinematic data is based on a kinematic model of the boom 31 and its actuation apparatus and the implement 24 and it actuation apparatus. The kinematic data utilizes a mathematical formulation that takes into account the structures of the actuation devices and lever arms being used to move boom 31 and the implement 24 as designed, in contrast to the actual positional data stored in memory 108 resulting from operation of the vehicle. The kinematic data is based on design parameters for the physical actuation devices and lever arms. Because physical devices are subject to manufacturing tolerances, the kinematic data does not always directly correspond to the sensed data. The difference between the sensed data and the kinematic data, also known as error data, is stored at memory 112. As used herein “kinematic” refers to theoretical distances/angles of the linkage.

On a material loading vehicle (such as the 4WD Loader), automated linkage control functions are often implemented. One such feature, known commonly as the “Return to Dig” feature, utilizes position sensors on the loader linkage to automatically return the front-end attachment to a position defined by the operator or by the manufacturer. Unless the position of the cylinder driving the front-end equipment is known (via in-cylinder position sensing), a system of at least two sensors, such as the boom sensor 64 and the implement sensor 66, is typically used to determine the position of the front end implement. A model of the linkage kinematics is used along with those two sensors to determine the position of all linkage elements. Any inaccuracy in these two or more sensors, however, potentially adds up the inaccuracies (also known as errors) and often results in a substantial error when directing the angular position of the front-end implement. Depending on tolerances for the various components that are built into the linkage systems and sensing system, minimizing the error by manufacturing methods to meet the customer requirements for the automated function may not be sufficient. For instance, to achieve accurate position of the boom and the work implement extremely tight manufacturing tolerances are required, but are not practically achievable due to the number of linkages and sensors requiring tight tolerances. In other situations, such tolerances, while achievable, are cost prohibitive. Consequently, minimizing the error in the hardware structures may not be possible or practicable.

The present disclosure includes a system having a calibration routine and a process to determine existing errors in a boom/implement system. The routine, however, is not limited to one type of implement, such as a bucket, and is also is used but not limited to other implements, such as a fork. By determining errors, any automated function control is compensated for by the determined errors that enables the boom and the implement to be positioned more accurately. On a loader linkage, for instance, the front-end equipment angular position error, in different embodiments, is a function of the boom height. Various boom positions generate different error stack-ups, where the errors add up in the two or more sensors used to calculate the front-end attachment position. To overcome the errors present in the loader linkage, the present system and process in one or more embodiments provides an error calibration routine to calculate a table of errors as a function of the boom position.

FIG. 5 illustrates a block diagram of a process 200 to determine angular position errors in a boom/work implement linkage and to use the determined errors to position the boom and/or work implement throughout the range of motion in either an automatic function or in manual control. The block diagram 200 discloses a process that calculates an error in the front-end equipment (work implement) position, wherein the calculation is based on or is a function of boom height. The calibration of the work implement position is made after a position sensor calibration routine. By calibrating the position sensors first, the determination of an error in the front-end equipment is made more precise. During a typical position sensor calibration routine, the boom is actuated between its fully lowered position and its fully raised position. The data taken at the two ends of travel are interpolated between the two end positions in order to determine a real-time position of the boom as it moves from one end of the range of motion to the other end of the range of motion. A similar calibration routine is performed for the front-end attachment. With these calibration points being identified, the positions of the boom and the front-end attachment are determinable in real-time.

The process of FIG. 5 begins at a start position 202 which begins after the operator turns on the work vehicle 10. Once the vehicle is running, the operator raises the boom 31 to a highest position such that the boom 31 is full raised at block 204. (See FIG. 3) In one embodiment, the display 110 of the user interface 40 displays a process start button, which is actuated by the operator to begin the routine. Once actuated, the display provides a series of steps to be completed by the operator. At a first step 204, the display instructs the operator to fully raise the boom 31 using one of the operator controls, such as the toggle. Once the boom is fully raised, the operator makes a selection from the user interface to indicate that the boom is in the fully raised position. In another embodiment, the controller 102 determines the fully raised position of the boom. Once the fully raised position has been identified, the controller 102 stores this position as a fully raised calibration point in the memory 106 including a sensor value generated by the sensor 64. Once stored, the display instructs the operator to fully lower the boom 31 using one of the operator controls at block 206. Once the boom is fully lowered, the operator makes a selection from the user interface to indicate that the boom is in the fully lowered position. (See FIG. 1) In another embodiment, the controller 102 determines the position of the boom at its lowest position. In other embodiments, the order of raising then lowering is reversed.

Once the fully lowered position has been identified, the controller 102 stores this position as a fully lowered calibration point in the memory 106 including a sensor value generated by the sensor 64. To fully lower the boom, the operator under most conditions tilts the work implement 24 toward the cab 12 to enable the boom to be fully lowered.

Once the highest and lowest position values of the boom are identified and stored, the display instructs the operator to fully tilt the work implement 24 in a first direction using one of the operator controls, such as the toggle. The operator, in most instances, raises the boom 31 sufficiently from the ground to enable complete rotational movement of the work implement 24 in either direction. (See FIG. 2) Once the work implement is fully tilted in the first direction at block 208, the operator identifies the first direction position with the user interface and the value of the sensor 64 is stored in memory as a first calibration point for a first full tilt value. In another embodiment, the controller 102 determines the position of the work implement and stores this value of the first direction position as a calibration point in the memory 106 at block 210. Once stored, the display instructs the operator to fully tilt the work implement 24 in a second direction using the operator controls at block 210. Once the implement is fully tilted (or rotated) in the second direction, the operator identifies the second direction position with the user interface and the value of the sensor 64 is identified and stored in memory as a second calibration point. In another embodiment, the controller 102 determines the position of the work implement and stores this second direction position as a calibration point in the memory 106 at block 210. In one or more other embodiments, the steps of 204, 206, 208, and 210 are either partially or completely automated by the controller 102. In the embodiment of FIG. 5, the display provides a calibration input device, such as a button, which upon selection by the operator, directs the controller 102 to move the boom from its lowest position to its highest position and to move the work implement from its fully tilted first position to its fully tilted second position.

After step 210, the boom sensor 64 and implement sensor 66 are now calibrated for the end of travel positions of the boom and the end of travel positions of the work implement. These values are stored in the memory 106. In one or more embodiments, the sensor 64 and the sensor 66 generate an output signal having a voltage representative of the position of the boom 31 and the work implement 24. In one embodiment for instance, each of the sensors 64 and 66 generates a signal having a voltage range of from 0.5 to 4.5 volts. The value at 0.5 volts is at one extreme location and the value at 4.5 volts is at the other extreme location. A halfway point between the two voltages, about 2.5 volts, indicates a center position of the boom 31 and of the work implement 24. Other types of sensors are contemplated.

Following the sensor calibration for sensors 64 and 66, an error (resulting from hardware tolerance stack-up) is determined by moving the boom 31 from the fully lowered position to the fully raised position, keeping the front-end attachment stationary. The front-end attachment angle (which is calculated as a function of the system of one or more sensors measuring linkage positions) is held constant throughout the range of boom travel. Consequently, any deviation of the work implement from the starting position is considered to be attributable to an error resulting from the sensing system and/or from the hardware. A storage table is generated, while the boom is being raised, to store one or more deviations from the starting position of the work implement with the sensed position of the work implement as the boom is raised. This deviation is identified as an error and stored as a function of boom height. The stored error is used by an automated function control routine to “offset” the setpoint for the front-end attachment based on the current boom position.

To determine the errors after the calibration of sensors 64 and 66, the operator is instructed by the system with a prompt displayed on the displayl10. The prompt instructs the operator to fully lower the boom 31 and to set the work implement 24 level with the ground 27 at block 212. This location is considered a “starting position”. Once lowered and the work implement is properly positioned, the operator acknowledges that the instructed location of the boom 31 and work implement 24 have been reached with an operator input to the display 110. In one embodiment, the display 110 includes a user input which is selected by the operator to confirm the proper position. Once acknowledged, the starting position for the work implement, that is determined by the controller based on inputs received by the sensors 64 and 66, is calculated based on, or as a function of, the calibration points identified after blocks 204, 206, 208, and 210. The calculated starting position is determined and stored in memory 106 at block 214. The starting position of the work implement, in one or more embodiments, is the angle of the implement that is set by the cylinder 28. The stroke of the rod of the cylinder 28 is set to a certain extension such that the cylinder rod extends from the cylinder body to position the implement at the starting position. In one example, the implement angle is 52 degrees at the starting position.

Once the stroke of the cylinder is identified and stored, the operator is instructed by the display to raise the boom 31 from its lowered position of block 212 to a fully raised position at block 216. As the boom 31 is raised (while the cylinder stroke position of the cylinder 28 is held constant), the values of the work implement sensor 66 and the values of the boom arm sensor 64 are received by the controller 102. As the boom is raised (or lowered in another embodiment from the highest position to the lowest position), the controller 102 stores the values received from the implement sensor 66 and the boom arm sensor 64 at predetermined locations of the boom arm as it moves from its lowest position to its highest position. At each of these predetermined positions, the sensed values of implement angle and boom angle provided by the sensors 64 and 66 to the controller 102 are identified and used to calculate an implement cylinder stroke value which represents an angle of the work implement with respect to the boom arm 31.

As the boom moves from the lowest position to the highest position, the angle of the implement changes due to the linkage kinematics. The value that is determined as a function of the sensors 64 and 66 at the starting position is the work implement cylinder stroke value or cylinder position, which does not vary as the boom is raised or lowered. This value of cylinder position, which also represents, the starting angle of the work implement, is used as a baseline for determining an error value during movement of the boom.

In one embodiment, the implement angles and boom angles determined by the sensors are used with kinematic data provided by a kinematic model of the boom and implement. These values are stored in memory 110 to determine the error between the starting position stroke value of the implement cylinder 28 (i.e. 52 degree implement angle in this example) with a calculated value of cylinder position using the boom and implement sensor values. Because of machine to machine variations due to manufacturing tolerances, the calculated value of cylinder position can and does vary when compared to the starting cylinder position. This error is calculated at every predetermined position and is stored as a calibration value in the memory 112. In one embodiment, the predetermined positions are identified at every 10% increment of movement of the boom 31 from its lowest position to its highest position at block 218.

As the boom is raised, the controller 102 receives a boom position signal from the boom sensor 64. The controller 102 determines at block 220 whether the boom has been raised by a 10% increment at block 220. If it has not been raised by 10%, the controller 102 continues to monitor the raising of the boom at block 218. If it has been raised by an increment of 10%, then the controller logs and stores a cylinder position error representative of the position of the work implement 24 at block 222. This error value is determined based on the previously stored starting position of the cylinder position that is subtracted from the currently identified position of the cylinder. At block 224 the controller 102 determines whether the boom 31 has been fully raised. If not, monitoring of the boom position continues at block 218. If the boom has been fully raised, the calibration is completed at block 226.

While the cylinder position error is stored for every 10% movement of boom height in FIG. 5, in other embodiments the cylinder position error is stored at other percentages of boom height. For instance, in one embodiment, the cylinder position error is stored for every 5% movement of boom height using the determined position of the implement with respect to the boom. Other percentages are contemplated.

In one or more embodiments, the cylinder position error, which correlates to a front end attachment error, is dependent upon the cylinder position at the starting position. For instance in one example, the starting position of a bucket is 52 degrees while the starting position of a fork is 60 degrees, each of which have a different cylinder stroke value. As such, in one embodiment, the calibration routine generates a two-dimensional table of errors that is dependent upon both boom height and cylinder stroke value. While such a calibration routine potentially provides a more accurate determination of errors, such a calibration routine requires additional time to complete a full calibration. By using a single position (the starting position in this example) of the cylinder stroke value, however, the calibration routine provides a determination of errors sufficient to accurately locate the work implement. In other embodiments, the calibration routine is automatically controlled to ensure that the cylinder stroke value does not change (by overriding the operator's ability to move it) as well as to limit the speed of the boom (in order to ensure calibration points are captured in a timely manner).

Once the error values are determined and stored in the memory 112 for each incremental boom height, those error values are used to position the work implement during a return to dig operation commanded by the operator. The return to dig user input 116, or return to dig user actuator, located at the user interface 40, is actuated by the operator when needed. During a return to dig operation, the controller 102 generates a boom position command, or boom adjustment signal, for movement of the boom 31, and generates a work implement command, or boom adjustment signal for movement of work implement 24 using the cylinder 28. In one or more embodiments, these position commands are based on the kinematic model of the positioning system which is generally the same for all work vehicles of a particular type. Each vehicle, however, can, and often is, different from another vehicle of the same type due to differences in manufacturing tolerances of the parts. Once the calibration routine is completed for a particular vehicle, the controller modifies the return to dig command for that vehicle based on the kinematic model with the determined calibration values 112. In this way, each vehicle is individually modified or customized to compensate for the particular structures of the parts used in the boom assembly and the work implement assembly.

The calibration routine is not limited to a return to dig operation, but is applicable to other functions of the work vehicle in which the calibrated errors are used to override normal operator commands. For instance, in one embodiment the calibrated errors are used in an auto leveling feature that automatically controls the level position of the work implement as the boom moves up and down. In this embodiment for a bucket, the bucket is rolled in and out at the boom is moved to keep the bucket level relative to the vehicle to ground. The error compensation is used to compensate the auto leveling feature to improve the precision of movement. Other functions are contemplated.

While exemplary embodiments incorporating the principles of the present invention have been disclosed hereinabove, the present invention is not limited to the disclosed embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of the invention using its general principles. For instance, while the hybrid power train controller and engine control unit are illustrated as separate devices, in other embodiments the hybrid power train controller and energy control device are embodied as a single device. Likewise, in other embodiments all control functions of a vehicle including the speed controller are embodied as a single device. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains. 

What is claimed is:
 1. A method of moving a work implement and a boom operatively connected a work vehicle supported by a surface, the work vehicle including a work implement sensor to determine a position of the work implement, and a boom sensor to determine a position of the boom, the method comprising: calibrating the work implement sensor; calibrating the boom sensor; raising the boom from a lowered position to a raised position; determining, with the boom sensor, a lowered position of the boom at the lowered position; determining, with the boom sensor, a raised position of the boom at the raised position; identifying a plurality of work implement positions while moving the boom from the lowered position to the raised position; identifying a plurality of error values based on the identified plurality of work implement positions; and moving the boom based on the plurality of error values during a work operation.
 2. The method of claim 1 wherein raising the boom step includes raising the boom from a fully lowered position to a fully raised position.
 3. The method of claim 2 wherein the raising the boom step further comprises raising the boom from the lowered position to the fully raised position while leaving the work implement stationary with respect to the boom.
 4. The method of claim 3 wherein the calibrating the work implement sensor includes: moving the work implement to a fully tilted position in a first direction; identifying the position of the work implement in the fully tilted position in the first direction.
 5. The method of claim 4 wherein the calibrating the work implement sensor includes: moving the work implement to a fully tilted position in a second direction; and identifying the position of the work implement in the fully tilted position in the second direction.
 6. The method of claim 5 wherein the raising the boom step includes fully lowering the boom to the fully lowered position and setting the work implement to a level ground position.
 7. The method of claim 6 wherein the identifying the plurality of boom positions includes identifying each of the plurality of boom positions at regularly spaced boom positions between the fully lowered position and the fully raised position.
 8. The method of claim 7 wherein the regularly spaced boom positions are spaced about every ten percent of a distance between the fully lowered position and the fully raised position.
 9. The method of claim 1 wherein the moving the boom based on the plurality of error values includes moving the boom in response to a return to dig operation.
 10. The method of claim 9 further comprising displaying on a user interface a return to dig actuator accessible by a user.
 11. A work vehicle comprising: a frame, a boom actuator including a boom arm, the boom actuator operatively connected to the frame, a work implement operatively connected to the boom arm; a boom sensor located at the boom actuator to identify a boom arm position of the boom arm with respect to the frame; an implement sensor located at the work implement actuator to identify a work implement position of the work implement with respect to the boom arm; a boom control device to provide a boom control signal; an implement control device to provide an implement control signal; a control module supported by the frame and operatively connected to the boom sensor, the work implement sensor, the boom actuator, the work implement actuator, the boom control device, and the implement control device, wherein the control module receives boom position signals from the boom sensor and work implement signals from the implement sensor, and transmits to the boom actuator a boom adjustment signal based on the boom position modified by a boom sensor calibration value and transmits to the implement actuator an implement adjustment signal based on the implement position modified by an implement sensor calibration value.
 12. The work vehicle of claim 11 further comprising a user interface including a return to dig actuator, wherein actuation of the return to dig actuator adjusts a position of the work implement with respect to the boom arm based on the boom sensor calibration value and the implement sensor calibration value.
 13. The work vehicle of claim 12 wherein the control module includes a processer and a memory, wherein the memory has a plurality of program instructions and a storage table to store error values based on a model of boom actuator kinematics and a model of implement actuator kinematics, that in response to execution by the processor causes the control module to determine the error values by: identifying a fixed position of the work implement with respect to the boom arm, wherein the fixed position of the work implement is determined by a position of the implement actuator; identifying, with the boom sensor, a position of the boom arm with respect to the frame at a plurality of positions between a fully lowered boom position and a fully raised boom position while maintaining the position of the work implement with respect to the frame; comparing the identified plurality of positions with the model of the boom actuator kinematics to arrive at the plurality of error values.
 14. The work vehicle of claim 13 wherein the user interface includes the boom control, the implement control, and a user input button operatively connected to the control module, wherein the user input button when selected by the user identifies and stores in the memory a lowest position of the boom and a highest position of the boom.
 15. The work implement of claim 14 wherein the processor causes the control module to display a user prompt to instruct the operator to move the work implement to the fixed position when the boom is fully lowered.
 16. The work implement of claim 15 wherein the return to dig actuator adjusts the position of the work implement using the plurality of error values.
 17. The work implement of claim 16 wherein the user interface includes an identify work implement user input to identify the type of work implement attached to the work vehicle.
 18. A method of positioning a work implement and a boom operatively connected a work vehicle, the work vehicle including a work implement sensor to determine a positon of the work implement, and a boom sensor to determine a position of the boom, the method comprising: calibrating the work implement sensor and the boom sensor; identifying an initial work implement position at a lowest boom position with the work implement sensor; identifying a plurality of boom positions while moving the boom from a lowest position to a highest position with the boom sensor; identifying a plurality of work implement positions with the work implement sensor at each of the plurality of boom positions while moving the boom from the lowest position to the highest position and while maintaining a position of the work implement with respect to the boom at the initial work implement position; comparing each of the identified plurality work implement positons with the initial work implement position to arrive at a plurality of work implement error values; and positioning the work implement with the boom based on the work implement error values during a work operation.
 19. The method of claim 18 wherein the calibrating the work implement sensor and boom sensor includes: i) identifying a first boom position at the lowest position with the boom sensor; ii) identifying a second boom position at the highest position with the boom sensor; iii) identifying a first work implement position at a first extreme position; and iv) identifying a second work implement position at a second extreme position opposite the first extreme position.
 20. The method of claim 19 wherein the positioning the work implement includes positioning the work implement in a response to a return to dig operation. 